The present invention concerns a catalyst comprising at least one catalytic element and a support comprising at least one 2:1 trioctahedral phyllosilicate containing fluorine, optionally and preferably bridged, at least one matrix and optionally, at least one Y zeolite with a faujasite structure. The invention also concerns a process for the hydroconversion of heavy petroleum feeds using this catalyst.
Hydrocracking of heavy petroleum feeds is a very important refining process which can produce lighter fractions such as gasolines, jet fuels and light gas oils from surplus heavy feeds which are not very valuable, which fractions the refiner needs in order to adapt production to market demands. In comparison with catalytic cracking, catalytic hydrocracking is intended to provide very high quality middle distillates, jet fuels and gas oils. In contrast, the gasoline produced has a much lower octane number than that from catalytic cracking.
Catalysts used for hydrocracking are all bifunctional, combining an acid function with a hydrogenating function. The acid function is provided by supports with large surface areas (150 to 800 m.sup.2.g.sup.-1 in general) with superficial acidity, such as halogenated aluminas (in particular chlorinated or fluorinated), combinations of boron oxide and aluminium, amorphous silica-aluminas and zeolites. The hydrogenating function is provided either by one or a plurality of metals from group VIII of the periodic classification of the elements such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by a combination of at least one metal from group VI of the periodic classification of the elements such as chromium, molybdenum and tungsten and at least one group VIII metal.
The balance between the two functions, acid and hydrogenating, is a fundamental parameter which governs the activity and selectivity of the catalyst. A weak acid function and a strong hydrogenating function result in catalysts which are of low activity, which operate generally at high temperatures (greater than or equal to 390.degree. C.) and at low space velocities (HSV expressed as the volume of feed to be treated per unit volume of catalyst per hour generally less than or equal to 2) but have very high selectivity towards middle distillates. In contrast, a strong acid function and a weak hydrogenating function produces very active catalysts but with poor selectivity towards middle distillates. The correct choice of each of these functions is the problem which must be solved in order to adjust the activity/selectivity couple of the catalyst.
It is thus of major interest in hydrocracking to have wide flexibility available on a number of levels: flexibility as regards the catalysts used, which results in flexibility in the feeds to be treated and in the products obtained.
The great majority of conventional hydrocracking catalysts are constituted by supports which are weakly acidic, such as amorphous silica-aluminas. Such systems are used to produce very high quality middle distillates and, when the acidity is very low, oil stock.
Amorphous silica-alurninas are weak acid supports. Many of the hydrocracking catalysts on the market are constituted by silica-alumina associated with either a group VIII metal or, as is preferable when the amount of heteroatomic poisons in the feed exceeds 0.5% by weight, an association of sulphides of metals from groups VIB and VIII. Such systems have very good selectivity towards middle distillates and high quality products are formed. For the most weakly acidic among them, such catalysts can also produce lubricant stock. As already stated, the disadvantage of all of such catalytic systems based on an amorphous support is their low activity.